1. Field of the Invention
The present invention relates to a resin-molding mold unit and a resin-molding apparatus provided with the resin-molding mold unit, and more particularly to the resin-molding mold unit and the molding apparatus both adapted to seal a semiconductor chip or like elements by molding of a resin.
2. Description of the Related Art
In a mass-consumption society of modern times, various types of products are mass-produced and mass-consumed. Consequently, an art of molding a resin is one of essential arts for supporting the mass-consumption society. A method for molding the resin has a wide variation. In a brief summary, the method is carried out by injection or potting of a molten resin in a mold. In this case, when an element such as a semiconductor chip or a like is previously disposed in the mold, it is possible to seal the element as a whole or to seal a part of the element by injection or potting of the resin (hereinafter referred to as a molding operation). In this molding operation, after completion of molding the resin, it is often difficult to take a molded product out of the mold. In order to avoid the above difficulty, a parting (demolding) agent is often used, which makes it possible to easily take the molded product out of the mold. Further, a suitable ejection means such as an ejection pin or a like is also used in the mold to serve as a mechanism for forcibly taking the molded product out of the mold after completion of molding the resin.
As shown in FIG. 7A, there is a conventional type of an ejection pin 103 in the art. The ejection pin 103 is movably mounted in a pin hole formed in the mold. In the molding operation, the ejection pin 103 has its front end portion slightly projected into a cavity of the mold by a length of from approximately 0.05 mm to approximately 0.20 mm. When the molded product is taken out of the mold, the ejection pin 103 is pushed into the cavity of the mold to have its front end portion largely extend into the cavity, so that the molded product is forcibly ejected from the mold. In general, as is clear from FIG. 7A, the conventional ejection pin 103 assumes a simple cylindrical shape with a full-diameter flat top surface.
As shown in FIG. 7B, there is another conventional type of an ejection pin 113 in the art, for example, as shown in Japanese Patent Application Laid-Open No. Hei 6-243641, wherein, as is clear from FIG. 7B, the other conventional ejection pin 113 has its front end portion formed into a circular truncated cone shape, a bottom diameter of which is smaller than an outer diameter of an intermediate portion of the ejection pin 113 to form a shoulder portion therebetween. In general, the ejection pin 113 is projected into the cavity of the mold by a length slightly longer than the above-mentioned ordinary length of from approximately 0.05 to approximately 0.20 mm applied to the front end portion of the previous ejection pin 103.
Ejection mechanisms such as one for taking the molded product out of the mold using the ejection pin provided in the mold are used not only in the art of resin-molding, but also in arts of metal forging, pressing, and like forming processes. These arts are described in, for example, Japanese Patent Application Laid-Open No. Hei 8-66737 and a like.
However, in a conventional resin-molding apparatus provided with the conventional ejection pins 103 or 113, the ejection pin has its front end portion extended into the cavity of the mold. This affects the molten resin in flow in the molding operation performed in the mold, and produces a void in the molded product. The thus produced void in the molded product impairs the product in appearance and sealing properties.
More specifically, as shown in FIG. 8A, in the case of the cylindrical ejection pin 103 provided with the full-diameter flat top surface, a molten resin indicated by a curved arrow xe2x80x9csxe2x80x9d joins at an opposite side of the ejection pin 103, and, therefore often forms an air trap xe2x80x9cvxe2x80x9d in a downstream side of the conventional ejection pin 103. Since the conventional ejection pin 103 has its top surface be smooth and parallel to an inner wall surface of the cavity of the mold, as shown in FIG. 8B, there is no possibility that the air trap xe2x80x9cvxe2x80x9d is removed by a molten resin xe2x80x9ctxe2x80x9d flowing over the top surface of the conventional ejection pin 103. As a result, the air trap xe2x80x9cvxe2x80x9d formed in the molten resin produces the above-mentioned void in the product thus molded.
As for the another conventional ejection pin 113 (shown in FIG. 7B) having its front end portion formed into the circular truncated cone shape with a reduced-diameter flat top surface, as is clear from FIGS. 9A and 9B, the air trap xe2x80x9cvxe2x80x9d is also formed in the downstream side of this conventional ejection pin 113, as is in the case of the previous conventional ejection pin 103. In this connection, since the conventional ejection pin 113 has its front end portion formed into the truncated cone shape smaller in volume than the corresponding front end portion of the previous conventional ejection pin 103, it is expected that the air trap xe2x80x9cvxe2x80x9d formed in the downstream side of this conventional ejection pin 113 is much smaller in volume than the corresponding air trap xe2x80x9cvxe2x80x9d formed in the downstream side of the previous conventional ejection pin 103. However, in the molding operation, the truncated cone-shaped front end portion of this conventional ejection pin 113 also serves as a part of the mold, and is therefore extended into the cavity of the mold by a length much longer than that of the corresponding front end portion of the previous conventional ejection pin 103. Consequently, an actual difference in volume between the air trap xe2x80x9cvxe2x80x9d formed by this conventional ejection pin 113 and the corresponding air trap xe2x80x9cvxe2x80x9d formed by the previous conventional ejection pin 103 is substantially negligible.
In view of the above, it is an object of the present invention to provide a resin-molding mold unit and a resin-molding apparatus provided with the mold unit, and more particularly to provide the mold unit and the molding apparatus both adapted to seal a semiconductor chip or like elements by molding of a resin, and thereby producing a molded product excellent in appearance and sealing properties.
According to a first aspect of the present invention, there is provided a resin-molding mold unit including:
a resin-molding mold member provided with a cavity assuming a predetermined shape, wherein said cavity is defined by an inner wall surface of said resin-molding mold member, and said inner wall surface is provided with a hole; and
a movable member which is movably mounted in said hole of said resin-molding mold member and has its front end portion formed into a semispheric shape.
In the foregoing, a preferable mode is one wherein said resin-molding mold member is further provided with an injection passage through which a molten resin is injected into said cavity of said resin-molding mold member.
Also, a preferable mode is one wherein said resin-molding mold member is integrally provided with a position control mechanism for controlling in position said movable member in a manner such that said movable member has an outer peripheral edge portion of its semispheric front end portion aligned in level with said inner wall surface which defines said cavity of said resin-molding mold member.
According to a second aspect of the present invention, there is provided a resin-molding apparatus for molding a molten resin into a predetermined shape, including:
a resin-molding mold unit comprising a first resin-molding mold member and a movable member, wherein said first resin-molding mold member is provided with a first cavity assuming a predetermined shape, wherein said first cavity is defined by an inner wall surface of said first resin-molding mold member, and said inner wall surface is provided with a hole, wherein said movable member is movably mounted in said hole of said first resin-molding mold member and has its front end portion formed into a semispheric shape, wherein said first resin-molding mold member is integrally provided with a position control mechanism for controlling in position said movable member in a manner such that said movable member has an outer peripheral edge portion of its semispheric front end portion aligned in level with said inner wall surface which defines said first cavity of said first resin-molding mold member;
a second resin-molding mold member provided with a second cavity which cooperates with said first cavity of said first resin-molding mold member to form a molding space into which said molten resin is injected and formed into a molded product; and
a movable member operating mechanism for operating said movable member in a manner such that: when said molten resin is injected into said molding space, said movable member is held in a position established by said position control mechanism; and, when said molded product is taken out of said molding space, said movable member is pushed forward to extend into said molding space to enhance demolding of said molded product.
In the foregoing second aspect, a preferable mode is one that wherein further including a mold unit operating mechanism for operating at least one of said first and said second resin-molding mold member so as to have said one brought into contact with and spaced apart from the other of said first resin-molding mold member and said second resin-molding mold member.
Also, a preferable mode is one wherein still further including an injection means for injecting said molten resin into said molding space, wherein said molding space is formed by both said first resin-molding mold member and said second resin-molding mold member.
With the above configurations, the mold unit operating mechanism operates at least one of the first and the second mold member, and thereby having their cavities combined with each other to form the molding space into which the molten resin is injected. At this time, the movable member operating mechanism keeps a length of the movable member exposed to the cavity of the mold at a predetermined value, which value has been determined by the position control mechanism to expose the above length of the movable member to the cavity of the mold. In other words, the movable member is controlled by the position control mechanism in a manner such that it has the outer peripheral edge portion of its semispheric front end portion aligned in level with the inner wall surface of the cavity of the mold member. In this condition, the movable member has only its semispheric front end portion projected into the cavity of the mold member. Incidentally, when the position control mechanism is combined with the mold unit to form a mold assembly by making the position control mechanism an integral part of the mold unit, it is possible to replace the mold assembly with a desired one of the mold assemblies without replacing the individual position control mechanism independently of the corresponding mold unit. In this case, it is possible to eliminate a position adjusting operation of the movable member even when the mold assembly is replaced with a desirable one.
In injecting the molten resin, the injection means or unit is actuated to inject the molten resin into the molding space of the mold unit. The thus injected molten resin flows along the front end portion of the movable member, so that the molding space of the mold unit in the vicinity of the front end portion of the movable member is filled with the molten resin.
As described above, the movable member has its front end portion formed into a substantially semispheric shape, and has the outer peripheral edge portion of this front end portion aligned in level with the inner wall surface of the molding space. In other words, the entire semispheric front end portion of the movable member projects into the molding space. Consequently, there is no gap between the inner wall surface of the molding space and the semispheric front end portion of the movable member. In other words, there is no fear that the molten resin flows into such gap to form a fin in the mold unit. Further, since only the semispheric front end portion of the movable member forms a projection in a stream of the molten resin in the molding space, any air trap is not formed in the downstream side of the movable member in the stream. Consequently, in the mold unit, it is possible to fill the molding space (particularly, a space in the vicinity of the front end portion of the movable member) with the molten resin without forming any air trap therein. In demolding the molded product from the mold unit after the molded resin is cured, the movable member operating mechanism is actuated to push the movable member into the molding space to enhance demolding of the molded product.